Safety device for presses



United States Patent 3,206,960 SAFETY DEVICE FOR PRESSES Bloss George Moxlcy, 5994 Grayton, Detroit, Mich. Filed Nov. 26, 1962, Ser. No. 239,983 11 Claims. (Cl. 721) This invention relates generally to presses, and refers more particularly to safety devices for presses.

It is an essential object of the invention to provide a safety device for a press which is operative to automatically withdraw one of the work-forming members of a press from its normal operative position in the event that there is an obstruction in the path of relative movement of one of the members. In other words, if the operator inadvertently puts his hand between the workforming members of the press during an operating cycle, the safety device of this invention is designed automancally to withdraw one of the work-forming members from its normal position so that the hand will not be injured. The obstruction might be something other than the op erators hand and might simply be a projecting portion of an improperly positioned workpiece.

Another object of the invention is to provide a press having a ram supported for movement toward a die structure to shape a workpiece, and means automatically operative to withdraw the die structure from its normal work shaping position in response to the presence of an obstruction in the path of the ram.

Another object is to provide a press wherein the die structure is supported by cams which are operated in response to the signal from a device for sensing obstructions carried by the ram.

Another object is to provide a press having a ram sup ported for downward movement toward the die structure to shape a workpiece, and means automatically operative during downward movement of the ram to lower the die structure away from its operative position when an obstruction is in the path of the ram.

Another object is to provide a press having cams for normally supporting the die structure in raised operative position, and hydraulic mechanism for operating the cams in response to a signal from the signal device on the ram.

Another object is to provide a press wherein the cams are pivoted links, the hydraulic mechanism is normally subjected to fluid pressure to locate the links in position to support the die structure in its raised operative position, and the automatically operative means etfects lowering of the die structure by relieving the fluid pressure on the hydraulic mechanism.

Another object is to provide a press having means for returning the die structure to its raised operative position automatically upon subsequent movement of the ram away from the die structure.

Another object is to provide means for cushioning the descent of the die structure toward inoperative position.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a fragmentary sectional view of a press embodying my invention, showing the press closed.

FIGURE 2 is similar to FIGURE 1 but shows the press open, with the die structure in its lowered inoperative position in solid lines and in raised operative position in dotted lines.

FIGURE 3 is a sectional view taken on the line 33 of FIGURE 2.

FIGURE 4 is a schematic wiring diagram.

Referring now more particularly to the drawing, the press comprises a base 1 supporting a lower die structure 2. The press also includes a ram 3 above the die struc 'ice ture supported for vertical movement toward and away from the die structure by guides 4. Any suitable means may be provided to reciprocate the ram between the upper limit of movement shown in FIGURE 2 and the lower limit shown in FIGURE 1.

The die structure 2 comprises a table 5 provided with an integral skirt 6 which is free to slide in a recess 7 in the base 1. The recess slidably receives the skirt 6 to permit the table 5 to move vertically between the raised operative position shown in FIGURE 1 and the lower inoperative position shown in solid lines in FIGURE 2.

The base is provided with a central hollow space 8 to accommodate the mechanism for supporting the table in raised position on the base. The supporting mechanism for the table comprises the cams 9, each of which is in the form of a link pivoted at one end to the fixed structure of the base by a pin 10. The other ends of the links are adapted to engage the underside 11 of table 5 to support it. The links are all of the same constructlon and preferably they are arranged in pairs with one pair at one end of the press and the other pair at the other end of the press.

The links 9 are operated by the hydraulic piston-cylinder assemblies 12, 13, 14 and 15. These assemblies are identical in construction and each comprises a cylinder 16 having a piston 17 reciprocable therein. Each cylinder is pivoted to the base 1 by a pin 18, and the rod 19 extendingfrom the piston is pivoted to a link 9 near the end of the link which supports the table by a pin 20. FIGURES l and 2 show a pair of links 9 at one end of the press which are respectively operated by the pistoncylinder assemblies 12 and 13. The pair of links at the other end of the press are related to each other and to the piston-cylinder assemblies 14 and 15 for operating them in the same manner as the links 9 shown in FIG- URES l and 2 are related to each other and to their operating assemblies 12 and 13.

The piston-cylinder assemblies are simultaneously operated, that is they are all either extended at the same time or retracted at the same time. FIGURE 1 shows the piston-cylinder assemblies extended, and this is ac-' complished by hydraulic fluid under pressure delivered to the head ends of the cylinders by hydraulic lines 22. FIGURE 4 shows the line 22 extending from the twoposition three-way valve 23. It will be understood that the line 22 in FIGURE 4 branches into four lines which respectively communicate with the head ends of the cylinders so that all of the piston-cylinder assemblies operate together. The reference numeral 24 indicates a line leading to the valve from a source of pressure and the numeral 25 leads from the valve to exhaust. Conse' quently, when the valve is shifted to one position it will place the respective cylinders in communication with the pressure line 24 to extend the piston-cylinder assemblies, as shown in FIGURE 1. Movement of the valve 23 to the other position will exhaust the cylinders through line 25, permitting the piston-cylinder assemblies to contract as in FIGURE 2. The valve 23 is normally positioned, as by a spring, to exhaust the cylinders. However, a solenoid 26 is provided to shift the valve 23 from its normal position to the position admitting fluid under pressure to the cylinders from line 24. The solenoid is effective to do this when energized.

The solenoid 26 is in a circuit 27 which includes an electric eye or photo-electric cell 28, a normally open trip switch 29, a relay 30 and a normally open relay contact 31 in a circuit 32 around the trip switch.

Referring again to FIGURES 1 and 2, it will be seen that the table 5 has a die 33 secured to its upper surface and provided with a die cavity 34. The ram 3 has a projecting part 35 which is adapted to extend into the die cavity and cooperate with it in the shaping of a workpiece. The die part 35 is of course vertically aligned with the cavity 34 so that it will register with the cavity when the ram is moved in a downward direction.

The ram also carries a safety mechanism 36 which extends downwardly from the ram to a point beneath the die 35. The safety device carries, the photo-electric cell 28 which is shown as comprising sending and receiving parts 37 and 38. The beam 39 from the sending part is received by the'receiver 38 to complete the circuit 27 across the photo cell. The beam 39 extends from one side of the die to the other and beneath the latter so as to be interrupted by any obstruction which might get in the way of the ram in its operating cycle. Actually a number of photo cells may be provided, similar to the one shown, but focusing a light beam at different angles across the ram so as to provide additional protection against the presence of an obstruction. The light beam shown in the present instance extends across the path of the ram at the loading zone. In other words, the beam 39 will be spaced laterally from the die parts a small distance toward the man who will load workpieces into the press so that he is protected against inadvertently placing a hand in the danger zone during the press cycle.

Springs 40 are provided in the recesses 7 which are shown in their normal unstressed condition in FIG. 1. These springs are provided to cushion or ease the descent of the lower die structure when it is withdrawn from operative position, and to support the withdrawn die structure.

The trip switch 29 is shown in FIGURE 2 having an operating lever' 42 in position to be engaged by a lug 43 on the ram at the upper limit of the ram. When the switch is thus operated, it is closed.

In normal operation, the circuit 27 to the solenoid 26 is closed, energizing the solenoid to shift valve 23 to a position admitting .fluid under pressure to the hydraulic cylinders 12-15. Accordingly, the die structure 2 is held in the elevated position of FIGURE 1, being supported by the links 9 which are held up by the extended piston-cylinder assemblies. The ram will 'move up and down between the upper limit of FIGURE 2 and the lower limit of FIGURE 1 in continuous cycles. At the upper limit, the operator may place a workpiece over the cavity in the lower die 33, being careful not to break the beam of light 39. Then, on downward movement of the ram the upper die 35 will enter cavity 34 and shape the workpiece. The light beam 39 will not, of course, be interrupted by the lower die structure because it 1s spaced to one side thereof.

- In the event the operator should break the beam of light with his hand, as might conceivably happen during the downward stroke of the ram, the circuit 27 will be opened de-energizing solenoid 26. As a result, the valye 23 will return to its normal position exhausting the piston-cylinder assemblies 1215 and permitting the lower die structure instantly to descend by gravity to the FIG- URE 2 position. The die structure will fall freely for a short distance before engaging the cushioning springs 40. In its lower inoperative position, the die structure 2 is spaced far enough-below the upper die 35 'that the operators hand will not be injured even at the lower limit of the ram. It will be understood, of course, that even a momentary opening of circuit 27 by the interruption of the beam of the photo cell will de-energize relay 30 and open relay contact 31 so that the circuit 27 cannot be reestablished until the normally open trip switch 29 is closed.

Upon the subsequent upward movement of the ram to gized relay 30. Accordingly, the die structure 2 will :be returned to its upper operative position shown in FIGURE 1.

The safety device does not interfere with the ram cycle. The ram continues to move through its normal cycle despite the presence of an obstruction in the beam of the photo cell. However, the presence of an obstruction in the beam of the photo cell will cause thedie structure 2 to be lowered by gravity, to its inoperative position and the die structure will not return to its operative position until the obstruction is removed from the beam of the photo cell and the trip switch 29 is closed. The movement of the die structure to its inoperative position is in a downward direction so that gravity acting on the heavy mass of the die structure effects an almost immediate withdrawal.

- While the springs 40 support the lower die structure 2 when it is withdrawn from the operative position, actually the piston-cylinder assemblies may assist in the support of the withdrawn die structure. In other words, in the withdrawn position of FIGURE 2, the heads of the pistons may engage abutments within the cylinders to support the die structure.

What I claim as my invention is:

1. In a press, a base, die structure, means for supporting said die structure on said base in an operative position, a ram, means supporting said ram for movement toward said die structure to shape a workpiece, and means automatically operative during the movement of said ram toward said die structure to withdraw said die structure from operative position in response to the presence of an obstruction in the path of said ram, said structure being withdrawn from operative position in a direction away from said ram and aligned with the path of movement thereof, the means for supporting said die structure on said base in operative position including a cam and mechanism for operating said cam, and the means for withdrawing said die structure including a signal device carried by said ram and controlling said mechanism.

2. In a press, a base, die structure, means for supporting said die structure. on said base in a raised operative position and in a lowered inoperative position, a ram above said die structure, means supporting said ram for downward movement toward said die structure while the latter is in raised operative position to shape a workpiece, and means automatically operative during downward movement of said ram to lower said die structure to inoperative position in response to the presence of an obstruction in thepath of said ram, the supporting means for said die structure including cams and hydraulic mechanism for operating said cams, and the means for automatically lowering said die structure including a signal device carried by said ram and controlling said mechanism.

3. The structure defined in claim 2, wherein said cams are pivoted links adapted to engage said die structure, said hydraulic mechanism is normally subjected to fluid pressure to pivot said links in one direction to positions supporting said die structure in its raised operative position, and said automatically operative means efiects lowering of said die structure by relieving the fluid pressure on said hydraulic mechanism permitting said links to pivotin the reverse direct-ion and thereby allow said die structure to descend by gravity.

4. In a press, a base, die structure, means for supporting said die structure on said base in a raised operative position and in a lowered inoperative position, a ram above said die' structure, means supporting said ram for downward movement toward saiddie structure while the latter is in raised operative position to shape a workpiece, means automatically operative during downward movement of said ram to lower said die structure to inoperative position in response to the presence of an obstruction in the path of said ram, and means for returning said die structureto its raised operative position automatically upon subsequent movement of said ram away from said die structure.

5. In a press, a base, die structure, means for supporting said die structure on said base in a raised operative position and in a lowered inoperative position, a ram above said die structure, means supporting said ram for downward movement toward said die structure while the latter is in raised operative position to shape a workpiece, means automatic-ally operative during downward movement of said ram to lower said die structure to in operative position in response to the presence of an obstruction in the path of said ram, and means for cushioning the descent of said die structure toward inoperative position.

6. In a press, a first member, means for supporting said first member in an operative position, a second member, means supporting said second member for movement toward and away from said first member and during its movement towards said first member said second member being operative to act upon a workpiece between said first and second members when said first member is in said operative position, means automatically operative during the movement of said second member towards said first member to withdraw said first member from operative position in response to the presence of an obstruction in the path of said second member, said first member being withdrawn from operative position in a direction away from said second member and aligned with the path of movement of said second member, the means for supporting said first member in operative position including a cam and mechanism for operating said cam.

7. The structure defined in claim 6, wherein the means for withdrawing said first member from operative position includes a signal device carried by said second member and controlling said mechanism.

8. In a press, a first member, mean for supporting said first member in an operative position, a second member, means supporting said second member for movement toward and away from said first member and during its movement toward said first member said second member being operative to act upon a workpiece between said first and second members when said first member is in said operative position, and means automatically operative during movement of said second member toward said first member to withdraw said first member from operative position in response to the presence of an obstruction in the path of said second member.

9. The structure defined in claim 8, wherein means are provided to return said first member to its operative position automatically upon the subsequent movement of said second member away from said first member.

10. The structure defined in claim 8, wherein said second member is movable vertically toward and away from said first member, and said first member is withdrawn from its operative position in a downward direction.

11. The structure defined in claim 10, wherein means are provided to cushion the downward movement of said first member during withdrawal thereof from operative position.

References Cited by the Examiner UNITED STATES PATENTS 2,338,329 1/44 Hermanns 1l334 FOREIGN PATENTS 852,037 10/52 Germany.

CHARLES W. LANHAM, Primary Examiner. 

1. IN A PRESS, A BASE, DIE STRUCTURE, MEANS FOR SUPPORTING SAID DIE STRUCTURE ON SAID BASE IN AN OEPRATIVE POSITION, A RAM, MEANS SUPPORTING SAID RAM FOR MOVEMENT TOWARD SAID DIE STRUCTURE TO SHAPE A WORKPIECE, AND MEANS AUTOMATICALLY OPERATIVE DURING THE MOVEMENT OF SAID RAM TOWARD SAID DIE STRUCTURE TO WITHDRAW SAID DIE STRUCTURE FROM OPERATIVE POSITION IN RESPONSE TO THE PRESENCE OF AN OBSTRUCTION IN THE PATH OF SAID RAM, SAID STRUCTURE BEING WITHDRAWN FROM OPERATIVE POSITION IN A DIRECTION AWAY FROM SAID RAM AND ALIGNED WITH THEPATH OF MOVEMENT THEREOF, THE MEANS FOR SUPPORTING SAID DIE STRUCTURE ON SAID BASE IN OPERATIVE POSITION INCLUDING A CAM AND MECHANISM FOR OPERATINGV SAID CAM, AND THE MEANS FOR WITHDRAWING SAID DIE STRUCTURE INCLUDING A SIGNAL DEVICE CARRIED BY SAID RAM AND CONTROLLING SAID MECHANISM. 